1. Field of the Invention
This invention relates to a belt conveyor and elevator system for lifting free-flowing, scatterable materials, such as granular materials, to an elevated location.
2. Description of the Prior Art
In a conventional belt conveyor and elevator system for lifting free-flowing materials, when such free-flowing materials, for example, granular, bulk solids, fall through a clearance that exists between the conveyor belt and a skirt during lifting and are accumulated on the back surface of the return-side portion of the conveyor belt, when the return-side portion of the belt is passed over the pulleys, the accumulated free-flowing material is pressed between the pulley and the belt and impedes the smooth travel of the belt. To prevent such accumulation, a partitioning plate has been provided between the carrier side and return-side portions of the conveyor belt.
For example, as shown in FIG. 6 in the prior art, a discharge opening D and a charging opening S open through an upper portion and a lower portion, respectively, of the casing H of a Z-type conveyor elevator having a rectangular cross-section. An endless conveyor belt B having a number of laterally extending carrier plates thereon extends around a drive pulley P.sub.1 and a driven pulley P.sub.2. A partitioning plate A is provided in the space between the upwardly moving side B.sub.1 and the downwardly moving side B.sub.2 of the conveyor belt B.
Accordingly, the free-flowing material that leaks and falls from the periphery of the carrier plates of the belt portion B.sub.1 during lifting of the free-flowing material, accumulates on the partitioning plate portion A' which is located below the horizontal section of belt portion B.sub.1 so as not to fall on the back surface of the horizontal section B.sub.2 ' of the belt portion B.sub.2.
The aforementioned prior art has the defect that the free-flowing, particulate material that accumulates on the partitioning plate portion A' has to be recovered frequently by scraping the partitioning plate portion A' by hand.
In a conventional belt conveyor and elevator system for lifting free-flowing particulate materials, a technique is disclosed, for example, in Japanese Utility Model Laid-Open No. 140323/1989, in which, as shown in FIG. 7, trapezoidal projections G having converging inclined surfaces project from the lower surface of the conveyor belt B adjacent to the opposite side edges thereof. The trapezoidal projections G fit into trapezoidal grooves of guide pulleys P which are fixedly mounted on a plurality of rotatable shafts mounted on and extending between opposite side plates of the casing H thereby to prevent lateral drifting or shifting movement of the belt B.
The aforementioned prior art has drawbacks in that the lateral drifting movement of the belt cannot be prevented unless the centers of the trapezoidal grooves of a number of the guide pulleys P are aligned in a straight line in the direction of the travel of the belt. The trapezoidal projections G cannot easily be mounted on the lower surface of the belt B at accurate fixed distances from both side edges of the belt and without being curved. When the belt B travels in a lateral drifting manner, the seal lip of the belt touches the seal recess of a skirt plate and becomes worn, thereby causing lowering of the seal performance.
A conventional anti-leaking device for free-flowing particulate material, in a belt conveyor and elevator system for lifting the free-flowing particulate material, as shown in FIG. 8, is disclosed in the aforementioned Japanese Utility Model Laid-Open No. 140323/1989.
FIG. 8 is a sectional view of the essential parts of a belt conveyor system in which an endless conveyor belt B is disposed within a closed-type casing H having a square cross-section. Mounted on the inner surface of an upper plate of the casing H is a trough T having a channel-shaped cross-section which trough forms a carrier passage for a number of lateral carrier plates P which are provided at equal intervals along the carrier surface of the conveyor belt B. The free end of the skirt plate T' of the trough T is positioned close to and slightly spaced from the side edges of the carrier surface on both sides of the belt B.
Anti-outflow, upright members D, adapted for hindering outflow of the free-flowing material and having an L-shaped cross-section, are mounted on the carrier surface close to both side edges of the belt B, in a slightly spaced relation to the outer surface of the skirt plate T' of the trough T. The top of the upright member D is slightly spaced from and is overlapped by a cover plate C which projects from the outer surface of the skirt plate T'.
Projections G projecting from the lower surfaces on both side edges of the belt B form trapezoidal guide rails which are fitted and guided in corresponding recesses of pulleys provided with grooves for carrying and guiding the belt B, as shown in FIG. 7.
In the aforementioned prior art, the clearance formed by the anti-outflow member D and the outer surface of the trough skirt plate T' is linear. Therefore, when the clearance between the top of the anti-outflow member D and the cover plate C increases, the free-flowing material that flows out between the free end of the skirt plate T' and the carrier surface of the belt easily overflows from the linear clearance through the top of the anti-outflow member D so that the free-flowing material is apt to leak outside the member D. This results in the difficulty that the height of the cover plate C needs to be vertically adjusted by means of a bolt S together with the skirt plate T' to minimize the clearance between the top of the anti-outflow member D and the cover plate C, but only to such an extent that they do not contact each other.